The Kiinde Kozii earned Editors' Choice thanks to impressive ease of use and health and safety scores. This warmer is a water bath warmer that heats contents slowly but consistently. It features a simple dial timer and a container area fit for most bottles or milk pouches. The Kozii has an innovative circulating water bath that controls water temperature via a thermostat, and at the end of the cycle, the water retracts into its reservoir. This warmer is one of the more expensive options, so it isn't the best choice for families on a budget. However, we think the consistent heat temperatures, versatile bottle size compatibilities, and user-friendly interface makes up for the higher price.
Kiinde Kozii Review
Pros: Water bath, user-friendly, versatile, timer in minutes
Cons: Expensive, no end of cycle beep, multiple cleaning steps
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Our Analysis and Test Results
The Kiinde company was founded by two MIT engineers (and dads) who envisioned an opportunity to improve infant feeding via a unique bottle warmer. From there, the line up expanded to a complete system that includes the Kiinde Squeeze baby bottle whose Kiinde Twist Pouch hooks up to any breast pump via a variety of adapters for direct pump-to-pouch expression. The uniquely designed Kiinde Keeper accents the system with a freezer storage solution designed to avoid bag puncture.
The Kozii (blue) earned a higher rank with top ease of use, cleaning, and health scores to help it along.
The sections below describe the Kozii performance during testing.
Health and Safety
The Kiinde Kozii earned a 9 of 10 for the health and safety. The warming chart with recommended settings helps to avoid overheating.
An innovative feature of the Kozii is an internal convection pump that sends water out of the reservoir to flow around the container. There is an overflow valve at the top where water flows back into the reservoir should the unit be filled higher than the "Full" indicator. At auto shut-off, water drains back into its reservoir which means heat is removed from the bottle when it shuts off, and users are less likely to contact warm water. However, like other warmers, if the heat is set too high, the Kozi can overheat milk.
The Kozii doesn't have an end of cycle beep; the timer has a "ticking" noise for 30 seconds at the end of the cycle, but it isn't loud enough. Even though water retracts into the reservoir, if a bottle remains inside the chamber, the milk temperature will continue to rise until removal.
The Kiinde warmer shuts off as it reaches 80F and then continues to warm gradually reaching no higher than body temperature when you follow the manufacturer's instructions. However, if you ignore the instructions and turn it to maximum and leave it running, the Kiinde will overheat bottle contents reaching 120F after 12 minutes. This temperature is both over the recommended temp for feeding and significantly over the 104F temperature when nutrients in breastmilk begin to degrade.
Ease of Use
The Kozii earned a 9 of 10 in ease of use. It is compact with a one-piece design. It comes with a Simple Start Guide, but we recommend reading the full manual and Troubleshooting Tips. Given the need for a warming chart, we wish it was attached to the device instead of in the manual where it could be misplaced.
The large reservoir has a 2 cup capacity that is easy to fill and can last between 5-10 uses. The timer dial is intuitive and shows how much time is left before shut off. All you need to do is fill the reservoir, and you are ready to go.
During warming, the chamber fills with warm, circulating water via an internal convection pump. In the end, just before it automatically shuts off, the water retracts back into the reservoir. To heat another bottle, you can start the unit right away, just be sure to reduce the heating time by 30 seconds.
We wish this warmer had an audible end of cycle beep. The 30 seconds of ticking at the end of the cycle, isn't loud enough and you can easily miss it.
The Kozii is slow warming earning it only 5 of 10 for this metric. Depending on the bottle material, quantity and starting temperature of the milk, it can take between 4 to 12 minutes to warm milk to body temperature.
It may take a trial period to find the right setting for your particular needs. Be patient. The extra time may be necessary to preserve breastmilk nutrients. Keep in mind, that frozen milk may take upwards of 12 minutes.
Always test the temperature of the contents before you give the bottle to your baby. After you remove the bottle from the warmer, you should gently swirl the bottle to remove any possible hot spots. Then you should drop some of the liquid on the inside of your wrist to ensure the contents aren't too hot. Your wrist is more sensitive than your fingers making it ideal for this use.
The Kozii executes warming consistently. In our testing, using the instructions, it took 4 ounces of refrigerated milk in a small Lifefactory Glass Bottle with silicone sleeve 5:30 to reach 80F and at maximum setting, 6:00 to reach 82F.
Ease of Cleaning
The Kozii has somewhat involved cleaning instructions earning a 6 of 10. Because this unit has a hidden reservoir, it is important to follow the cleaning instructions to avoid mold growth and hard mineral build-up inside. The overall instructions are detailed, and you'll need the manual for regular referencing.
- Every 2 to 3 Days — Rinse the inside reservoir with mild soap/water solution and wipe chamber and outside with wet, soapy sponge. Air dry.
- Every 2 Weeks — Perform the above using 1:50 bleach solution instead of soap. Fill the Kozii completely including the overflow drain and let it sit for 10 minutes. Rinse three times and run the unit with 2 cups of fresh water for 3 minutes.
- Every 2 Months — Descale with 1/2 cup white vinegar: 1 cup cold water and pour into the chamber. Let stand for 10 to 20 minutes with unit unplugged. Pour the vinegar solution out via overflow drain. Rinse with fresh water three times swirling gently.
— Juliet Spurrier, MD and Wendy Schmitz